1. Field of the Invention
The invention relates to a scraper for determining the position of pipelines and having at least one scraper body and support elements located on its outer circumference for guidance in the pipeline, the scraper body containing a gyroscopic platform, as well as supply and a processor for the measured results.
2. Description of the Prior Art
Such surveying scrapers known as gyroscopic scrapers are e.g. used for surveying the route of old, existing pipelines, where the precise path thereof in the countryside is unknown. The data collected by the scraper are transformed on evaluation into a known coordinate system, so that the precise space coordinates are known for every point along the pipeline route. If desired, this information can be used in an accurate map for the plotting of the route. In addition, such scrapers are used for discovering faults in pipelines and then additionally cooperate with so-called intelligent scrapers. For discovering faults use is made of the data supplied by the measurements of the gyroscopic scraper, in order e.g. in a so-called GPS system, to rapidly and easily locate the correct fault along the pipeline route.
Another field of use is the determination of local position changes, because e.g. in areas with unstable terrain, such as e.g. abrupt slopes, pit subsidence areas, areas with drifting sand or permafrost soil, the pipeline position can change as a result of earth movements, so that serious stresses occur in the pipe, which in an extreme case can lead to folding or even fracture of the pipe. When surveying such pipelines at regular intervals with a gyroscopic scraper, these position changes can be roughly determined, in order to calculate the stresses which have built up in the pipeline. On reaching specific stress levels, countermeasures can be initiated, before more serious damage occurs.
In order to be able to carry out such surveys, the scraper has a pressure-resistant body for receiving the electronics and measuring equipment, as well as support elements for guiding on the inner wall of the pipeline to be surveyed. In addition, a gyroscopic platform is installed in the pressure-resistant body, together with the data processing electronics and the mass memory. For path measurement purposes, such a scraper has several odometer systems and by means of a marker system fixed points are set along the pipeline. After passing through the pipeline, the data are then taken from the scraper and evaluated with special software programs. In order that the data provide valid information, the gyroscopic platform must be guided in a uniform position parallel to the pipe axis or wall. In practice it means that the precise position of the scraper body axis relative to the pipe axis must be known. The measured results are falsified if this position is changed. Normally the scraper bodies are guided in the pipeline by means of collars or rollers as support elements. As the pipe diameter is not always constant, the support and guidance elements must be sufficiently flexible for them to be able to compensate diameter changes. In the case of collars this is brought about by the rubber-like flexibility of the material, whereas in the case of a roller guide, the rollers are suspended on spring-loaded, bend-in arms. As a result of the propelling force acting from the rear when the scraper travels through the pipeline, the scraper has a dynamic buckling tendency, so that the angle between the scraper axis and the pipe axis does not remain constant during travel or running. If the support elements are scraper collars or sleeves, it is also possible for there to be a change in the position of the scraper body relative to the pipe axis due to wear to such collars or sleeves.
Therefore a scraper has already been proposed, in which there is an additional arrangement of ultrasonic sensors in annular manner both at the front and rear of the scraper body, so as to constantly measure the distance from the pipe wall. When evaluating the data, the distance information is utilized in order to establish the position of the scraper body or its axis relative to the pipe axis and perform corresponding corrections. As a result of this additional technical expenditure, the manufacture of the scraper is made much more expensive and the necessary correction during evaluation also increases time expenditure and therefore costs.
The problem solved by the invention is to provide a scraper of the aforementioned type which, in the case of a simpler and cheaper manufacture, provides precise information on the position of the scraper body axis relative to the pipe axis.
The embodiment of the prior art scraper 1 shown in FIG. 1 has a scraper body 2 with a pressure-resistant casing. The casing of the scraper body 2 is surrounded by a conical, flexible material sleeve 3, 3' at the front and rear, axial end of the scraper body. By means of the sleeves 3, 3' serving as support and guidance elements, the scraper 1 is guided through a pipeline 4. The free ends of the sleeves 3, 3' engage on the pipe inner wall. As can be gathered from FIG. 1, as a result of the propelling force acting from the rear and which is indicated by the arrow B, the scraper 1 has a dynamic buckling tendency, so that the angle .alpha. between the scraper axis M and the pipe axis R no longer remains constant.
As within the scraper body 2 are installed and fitted a gyroscopic platform, together with data processing electronics, a mass storage memory and a power supply 30. The dynamic buckling of the scraper 1 results in the gyroscopic platform no longer having the necessary uniform position parallel to the pipe axis or wall, so that the data obtained no longer provide valid information.